Abstract

Background

Due to the absence of a current and validated food frequency questionnaire (FFQ) for
use in New Zealand adolescents, there is a need to develop one as a cost-effective
way to assess adolescents’ food patterns. This study aims to examine the test-retest
reliability and relative validity of the New Zealand Adolescent FFQ (NZAFFQ) to assess
food group intake in adolescents aged 14 to 18 years.

Methods

A non-quantitative (without portion size), 72-item FFQ was developed and pretested.
Fifty-two participants (aged 14.9 ± 0.8 years) completed the NZAFFQ twice within a
two-week period for test-retest reliability. Forty-one participants (aged 15.1 ± 0.9
years) completed a four-day estimated food record (4DFR) in addition to the FFQs to
enable assessment of validity. Spearman’s correlations and cross-classification analyses
were used to examine relative validity while intra-class correlations were additionally
used for test-retest reliability.

Results

Weekly intakes were estimated for each food item and aggregated into 34 food groups.
The median Spearman’s correlation coefficient (SCC) between FFQ administrations was
0.71. SCCs ranged from 0.46 for fruit juice or cordial to 0.87 for non-standard milk. The median intra-class correlation coefficient (ICC) between FFQ administrations
was 0.69. The median SCC between food groups from the FFQ and the 4DFR was 0.40 with
the highest SCC seen for standard milk (0.70). The exact agreement between the methods in ranking participants into thirds
was highest for meat alternatives (78%), but lowest for red or yellow vegetables and potatoes (27%). The mean percent of participants misclassified into extreme thirds for food
group intake was 12%.

Conclusions

Despite a small sample size, the NZAFFQ exhibited good to excellent short-term test-retest
reliability and reasonable validity in ranking the majority of the food group intakes
among adolescents aged 14 to 18 years. The comparability of the validity to that in
the current literature suggests that the NZAFFQ may be used among adolescent New Zealanders
to identify dietary patterns and rank them according to food group intake.